Mobi-Sync: Efficient Time Synchronization for Mobile Underwater
Sensor Networks
Abstract:
Time synchronization is an important requirement for many services provided by distributed
networks. A lot of time synchronization protocols have been proposed for terrestrial Wireless
Sensor Networks (WSNs). However, none of them can be directly applied to Underwater Sensor
Networks (UWSNs). A synchronization algorithm for UWSNs must consider additional factors
such as long propagation delays from the use of acoustic communication and sensor node
mobility. These unique challenges make the accuracy of synchronization procedures for UWSNs
even more critical. Time synchronization solutions specifically designed for UWSNs are needed
to satisfy these new requirements. This paper proposes Mobi-Sync, a novel time synchronization
scheme for mobile underwater sensor networks. Mobi-Sync distinguishes itself from previous
approaches for terrestrial WSN by considering spatial correlation among the mobility patterns of
neighboring UWSNs nodes. This enables Mobi-Sync to accurately estimate the long dynamic
propagation delays. Simulation results show that Mobi-Sync outperforms existing schemes in
both accuracy and energy efficiency.
Existing System:
This paper addresses the time synchronization problem, a critical service in any sensor network.
Nearly all UWSN applications depend on time synchronization service. For example, data
mining requires global time information, TDMA, one of the most commonly used Medium
Access Control (MAC) protocols, often requires nodes to be synchronized. Furthermore, most of
the localization algorithms for underwater and terrestrial sensor networks assume the availability
of time synchronization service. Numerous times synchronization protocols for terrestrial
Wireless Sensor Networks (WSNs) have been proposed in the literature synchronization
accuracy and energy efficiency for land-based applications is cogent. However, most of these
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approaches assume that the propagation delay among sensors is negligible. This is not the case in
UWSNs, which suffer from the low propagation speeds of acoustic signals (roughly 1,500 m/s in
water). Sensor node mobility also contributes to long and variable propagation delay in UWSNs.
These additional complicating factors render previous approaches less suitable for adaptation to
UWSNs. Furthermore, the batteries of underwater sensor nodes are difficult to recharge and it is
often impractical to replace due to their relative inaccessibility. This lack of serviceability
imposes even more stringent requirements. The UWSN will need to be energy efficient. This set
of distinguishing characteristics introduces new challenges into the design of time
synchronization schemes for UWSNs.
Disadvantages Of Existing System:

Low communication bandwidth, long propagation delays, higher error probability, and
sensor node mobility.

The batteries of underwater sensor nodes are difficult to recharge and it is often
impractical to replace due to their relative inaccessibility. This lack of serviceability
imposes even more stringent requirements.

The UWSN will need to be energy efficient. This set of distinguishing characteristics
introduce new challenges into the design of time synchronization schemes for UWSNs
Proposed System:
This paper proposes Mobi-Sync, a high energy efficient time synchronization scheme
specifically designed for mobile UWSNs. The distinguishing attribute of Mobi-Sync is how it
utilizes information about the spatial correlation of mobile sensor nodes to estimate the long
dynamic propagation delays among nodes. The time synchronization procedure consists of three
phases: delay estimation, linear regression, and calibration. Phase I acquires information about
the spatial correlations of the mobile sensor nodes to accurately estimate the propagation delays.
In Phase II, sensor nodes perform linear regression based on MAC layer time stamps and
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corresponding propagation delays to produce initial estimates of the clock skews and offsets.
These initial results serve as inputs to Phase III, which calibrates the estimates, further improving
the synchronization accuracy. During calibration, the final clock skew and offset estimates are
obtained by updating certain parameters and repeating the delay calculations and linear
regressions. Extensive simulations demonstrate the effectiveness of the proposed approach for
time synchronization, confirming that it does not suffer from mobility. The results indicate that
MobiSync outperforms existing schemes with respect to both accuracy and energy efficiency
Advantages Of Proposed System:
Extensive simulations demonstrate the effectiveness of the proposed approach for time
synchronization, confirming that it does not suffer from mobility. The results indicate that
MobiSync outperforms existing schemes with respect to both accuracy and energy efficiency.
System Configuration:Hardware Requirements:-
 Processor
-Pentium –III
 Speed
- 1.1 Ghz
 RAM
- 256 MB(min)
 Hard Disk
- 20 GB
 Floppy Drive - 1.44 MB
 Key Board
 Mouse
 Monitor
- Standard Windows Keyboard
- Two or Three Button Mouse
- SVGA
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Software Requirements:-

Operating System
: WINDOWS XP

Front End
: C#.NET

TOOL

Database
: VISUAL STUDIO 2008
: SQL SERVER 2005
Reference:
Jun Liu,Student Member, IEEE Computer Society, Zhong Zhou, Member, IEEE Computer
Society, Zheng Peng,Member, IEEE Computer Society, Jun-Hong Cui, Member, IEEE
Computer Society, Michael Zuba,Student Member, IEEE Computer Society, and Lance
Fiondella,Member, IEEE Computer Society “Mobi-Sync: Efficient Time Synchronization for
Mobile Underwater Sensor Networks” IEEE TRANSACTIONS ON PARALLEL AND
DISTRIBUTED SYSTEMS, VOL. 24, NO. 2, FEBRUARY 2013.
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